Medical Devices Comprising Nanocomposites

ABSTRACT

The present invention provides medical devices comprising nanocomposite materials. By utilizing nanocomposites in the production thereof, the inventive medical devices can be produced with various advantageous properties. Methods of producing the inventive medical devices are also provided. Inasmuch as the inventive devices are expected to provide certain advantages in their use, there is also provided a method of medical care including methods of treatment or diagnosis, wherein the inventive devices are brought into therapeutic contact with a body to be treated or diagnosed thereby.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 10/259,545, filed Sep. 27, 2002, which claims the benefit ofpriority of U.S. Provisional Patent Application Ser. No. 60/331,332,filed Sep. 28, 2001, and U.S. Provisional Patent Application Ser. No.60/327,629 filed Oct. 5, 2001, the entire disclosures of which are allhereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to medical devices including one or morecomponents comprised of one or more nanocomposite materials. Byutilizing nanocomposites in the manufacture of the inventive medicaldevices, certain properties of the nanocomposites may be exploited inways particularly advantageous in the medical device industry.

BACKGROUND OF THE INVENTION

The medical device industry is but one example of an industry where theproducts or devices produced and used therein requires the products toexhibit a diverse array of properties. Transluminal medical devices areone example. Such devices are typically introduced into the vasculatureof a patient at a point remote from the treatment site, a procedure thatcan be uncomfortable for the patient. In order to perform acceptably,and to minimize the trauma to the patient, transluminal devicestypically exhibit diverse, and at times divergent, performancecharacteristics. For example, many such devices desirably exhibit goodmaneuverability so as to be manipulated to and/or inserted at a locationrequiring treatment, but yet sufficiently strong in the longitudinaldirection so as not to buckle or kink when being so manipulated. Infact, many medical devices require a combination of these, and other,properties such as strength, thermal stability, structural stability,flexibility, opacity, radio-opacity, storage stability, lubricity,stability to sterilization treatment, etc., in order to be effective fortheir intended purpose.

Material selection is thus very important to the therapeutic efficacy ofmany medical devices since the properties of the materials used oftendictate the properties of the overall device. However, the range ofproperties available from one, or even a combination of, material(s) isoften not as broad as would be desired in medical device applications.As a result, many medical devices need to be manufactured from acombination of materials, processed in a specific manner, coated, orsubjected to other treatments, in order to exhibit the desired and/orrequired characteristics.

Thus, there is a continuing need in the medical device industry todevelop or discover additional materials that exhibit the range ofproperties required for a medical device.

SUMMARY OF THE INVENTION

The present invention provides medical devices comprising nanocompositematerials. According to the invention, utilization of nanocomposites formedical devices can provide the devices with many, or all, of thediverse properties often desirable in the same. That is, inasmuch assuch devices often desirably exhibit a vast number of oftentimesdivergent properties, it can be difficult to manufacture such deviceswithout utilizing an extensive number of materials and processingtechniques. By employing the present invention, however, medical devicescan be produced with a desired array of properties using a lesser amountof materials and/or processing techniques, or medical devices can beproduced wherein one or more of the properties are enhanced.

As a result, the present invention provides a medical device comprisingat least one nanocomposite material. The nanocomposite material(s) maydesirably be employed to produce one or more components of the device,or may be utilized to produce the device in total. The nanocomposite isdesirably comprised of a matrix material and at least one plurality offiller particles. In some embodiments, the nanocomposite may comprise amatrix including a first plurality of filler particles comprised of afirst material and at least one other plurality of filler particlescomprised of a second material.

Also provided is a method of making the inventive medical deviceswherein the method comprises selecting the nanoparticulate filler,selecting the matrix material, preparing a nanocomposite from the fillerand matrix material, and preparing at least a component of the medicaldevice from the nanocomposite material. Exemplary medical devices towhich the invention is particularly directed include balloons,catheters, filters and stent delivery systems such as disclosed in U.S.Pat. Nos. 5,843,032; 5,156,594; 5,538,510; 4,762,129; 5,195,969;5,797,877; 5,836,926; 5,534,007; 5,040,548; 5,350,395; 5,451,233;5,749,888; 5,980,486; and 6,129,708, the full disclosures of each ofwhich are hereby incorporated by reference herein for all purposes.

The inventive medical devices can have enhanced properties relative to,or properties absent from, a corresponding medical device not comprisinga nanocomposite material. As a result, the inventive medical devices canprovide certain advantages in their use. In this regard, the presentinvention also provides a method of treatment or diagnosis comprisingbringing a medical device into therapeutic contact with a body to betreated or diagnosed, wherein the medical device comprises at least onenanocomposite material.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this application, illustrate several aspects of the inventionand together with the description of the embodiments reserve to explainthe principles of the invention. A brief description of the drawings isas follows:

FIG. 1 is a longitudinal cross-sectional view of the distal end of amedical device in accordance with the present invention;

FIG. 2 is a transverse cross-sectional view of the device shown in FIG.1, taken at line 2-2; and

FIG. 3 is a longitudinal cross-sectional view of the distal end of amedical device in accordance with the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The embodiments of the present invention described below are notintended to be exhaustive or to limit the invention to the particularembodiments disclosed in the following detailed description. Rather, theembodiments are described so that others skilled in the art understandthe principles and practices of the present invention.

The present invention provides medical devices including at least onecomponent comprised of at least one nanocomposite material. Theinvention can be particularly advantageous when applied to medicaldevices contemplated for either temporary or permanent treatment of theheart and/or circulatory system. For example, for treatment devices(such as an angioplasty catheter, angiography catheter, stent deliverysystem, etc.) the device desirably provides sufficient “pushability”that force applied at the proximal end is transmitted to the distal endto guide the distal end to the desired site. Such devices are alsodesirably “trackable” so that a positional movement, as to the right orthe left, upward or downward, exerted by the operator at the proximalend translates to the desired motion at the distal end. Such devices arealso desirably flexible enough so that when traversing a narrow andoften tortuous space to get to the desired site, the device does notcause substantial injury to the surrounding tissue. Finally, it is oftendesired that the outer surface, or inner surface, of these devices besufficiently lubricious so as to be easily passed over a guidewire andthrough the body to the desired site.

Devices intended to be used for a substantially permanent treatment havea corresponding number of desirable and yet diverse properties. Forexample, devices intended for implantation into the heart or vasculatureto repair or replace certain parts thereof, such as artificial heartvalves, artificial veins and arteries, or stents, desirably exhibitrobust mechanical strength, and are yet flexible enough, to withstandthe periodic yet continual contractual environment in which they mustnot only exist but function. The devices may also desirably besubstantially nonthrombogenic due to the extended period of time thesedevices are contemplated to be resident within the body. Furthermore, incertain applications, such devices may desirably be biodegradable.

In order to achieve a combination of desired properties, more than onetype of material is often employed in the construction of medicaldevices. For example, reinforcing filler particles can be added to amatrix material to form a composite material having a desired modulus,i.e., by acting as stress transmission elements and/or by concentratingor increasing the strain within the matrix material. Conventionally, thefiller particles used in such composites are comprised of glass fibers,aggregates of amorphous or graphitic carbon, metal flakes, etc., and areat least about 1 micrometer in diameter in their largest dimension orlarger. While such composite materials are useful in many medical deviceapplications, the tolerances for many other medical device applicationsmay not accommodate conventional, large size, filler particles.

Recently, a new class of filler particles has been described having atleast one dimension less than about 1 micrometer. Filled polymer systemswhich contain such nanostructured particles have been termednanocomposites. It has now been appreciated that these new materials canprovide many unique advantages in the production of medical devices inaccordance with the present invention. The use of nanocompositematerials in the manufacture of the inventive medical devices mayprovide the ability to control the modulus of a nanocomposite materialwhile not affecting the processability thereof. Further, the use ofnanocomposites may provide these advantages without substantiallynegatively impacting the compatibility between the nanocomposite andother materials that may be used in the manufacture of the medicaldevice. Finally, by combining nanocomposites with other non-compositematerials, it may be possible to control the directionality of change inthe physical properties.

In addition to tailoring physical properties in small dimensions,nanocomposites may offer other significant advantages in medical deviceapplications. For example, since in many cases the size of thenanofiller particle is smaller than the wavelength of visible light, itis possible to use nanocomposite materials to achieve the aforementionedadvantages, while yet providing a transparent material. Such transparentnanocomposite materials could be useful, for example, to provide X-rayradiopaque materials that are optically clear. Other advantages uniqueto the use of nanocomposites in medical devices may include effects suchas lowering the coefficient of friction, providing biocompatibility, andimparting biodegradability, to name a few.

Also, and without being limited to a particular theory, it is believedthat because of the size of the nanoparticles, there is increasedsurface area contact between the filler particles and the matrixmaterial in a nanocomposite as compared to a traditional filled polymer.This effect may be further enhanced by utilizing filler particles thatare not only smaller than traditional filler particles, but also, thathave high aspect ratios, i.e., a large ratio of their lateral dimensionas compared to their thickness. Properties as good or better may thus beachieved in a nanocomposite as compared to the corresponding traditionalfilled polymer, while utilizing less filler material. Not only areperformance and quality control significantly enhanced, cost savings canbe seen that can be an important advantage in many medical deviceapplications.

The term “nanocomposite”, as used herein, generally refers to acomposite material comprising a matrix material and a plurality offiller particles, wherein the filler particles are smaller than thoseutilized in conventional filled composites. More particularly, the term“nanocomposites” includes a matrix material comprising at least oneplurality of filler particles having at least one dimension less thanabout 1000 nm in size. In some embodiments, the filler particles arebetween about 1 nm and 100 nm. Advantageously, nanocomposite materialscan be engineered so that the nanocomposite exhibits the same propertiesas the matrix material to an enhanced degree and/or exhibits propertiesin addition to those exhibited by the matrix material alone. Utilizingnanocomposite materials in the manufacture of one or more components ofmedical devices may allow certain properties of the nanocomposites to beexploited in ways particularly advantageous in the medical deviceindustry.

Any medical device can benefit from the application of the inventiveconcept of the present invention. As a result, the choice of the medicaldevice in which to apply the concept is not particularly limited. It isbelieved, however, that the inventive concept will prove particularlyadvantageous when utilized in medical devices contemplated to be broughtinto therapeutic contact with a body, i.e., devices contemplated to beintroduced into the body, either temporarily or permanently, for thepurpose of effectuating a treatment or diagnosis thereof. Such devicesfind use in, e.g., urinary, cardiovascular, musculoskeletal,gastrointestinal, or pulmonary applications. Medical devices useful inurinary applications include, for example, catheters, shunts, stents,etc. Exemplary medical devices useful in cardiovascular applicationsinclude stents, angiography catheters, coronary or peripheralangioplasty catheters (including over the wire, single operator exchangeor fixed wire catheters), balloons, guide wires and guide catheters,artificial vessels, artificial valves, filters, vascular closuresystems, shunts, etc. Musculoskeletal medical devices include, forexample, artificial ligaments and prosthetics. One example of a medicaldevice useful in a gastrointestinal application would be a shunt.Pulmonary medical devices include prosthetics, as one example.

One example of a particular application in which the invention can beadvantageously used is that of transluminal medical devices. Suchdevices include, e.g., catheters (e.g., guide catheters, angioplastycatheters, balloon catheters, angiography catheters, etc.) shunts,stents and stent delivery systems (e.g., self-expanding and balloonexpandable), filters, etc. These devices often include extrudedcomponents made up of one, two, three, or more layers of materials.According to the invention, such devices include at least onenanocomposite material. That is, certain components of the device caninclude nanocomposite and non-nanocomposite materials. If multiplelayers are used, at least one layer can be a nanocomposite material. Thenumber and organization of the layers can be chosen to effectuate and/orto provide properties desired in the device. Further, in someembodiments, the quantity of filler particles of the nanocompositematerial can vary at different regions of the nanocomposite. Such analteration in the filler density can, for example, provide a device thathas varying properties, such as flexibility, along its longitudinalaxis.

In one exemplary embodiment, the medical device can be a catheter shaftsuch as for an angiography system, angioplasty balloon, guide catheter,or stent delivery system. Such devices often include multiple lumens ina side-by-side or coaxial configuration. Coaxial configurationsgenerally have more than one lumen, wherein the lumens are typicallyfixed relative to one another and may be provided as coextruded singlecomponents, or may be separately extruded and then assembled by anyconventional construction method to provide a multiple lumen structure.According to the invention, any of, or all of, the tubular componentsproviding such a multiple lumen structure can be formed from ananocomposite material. In some embodiments, the tubular component canbe comprised of a plurality of layers wherein at least one layer of thetubular wall is a nanocomposite material. In such devices, the numberand organization of the layers can be chosen to effectuate and/orprovide the properties desired in the multilayer tubular component.Further, the dimensions of the device can be varied. For example, thelayers of a multilayered tubular wall can have a diverging or convergingtaper from the proximal end to the distal end of the wall.

As but one particular example of the embodiment of the invention whereinthe medical device is a catheter shaft, conventionally reinforced withsteel braiding, the catheter shafting may alternatively andadvantageously be prepared utilizing a nanocomposite comprising, forexample, ceramic nanofibers as the filler particles. Inasmuch as such ananocomposite can be processed using normal extrusion processes,intermittent extrusion and/or multi-layer extrusion can be used toselectively include the ceramic nanofibers in order to furtherselectively stiffen areas of the shaft. Further advantageously, theceramic nanofibers may be oriented, if desired, by employing rotating orcounter-rotating extrusion, which orientation can provide enhancedtorque performance of the shaft. If such orientation is not desired,ultrasonic vibrations can be introduced into the extrusion process inorder to obtain a more randomized ceramic nanofiber orientation. Inaddition to these processing advantages, such shafting, while providingcatheter shafting with a desired degree of reinforcement, would also beuseful in MRI applications.

The nanocomposite material to be used in the present medical devices isnot particularly restricted. Rather, any nanocomposite that can beengineered to display at least one of the properties desired in thedesired medical device can be used. As is the case with the overallnanocomposite material, the material(s) that may be used as either thematrix material or the filler particle material is not restricted.Rather, nanocomposites to be utilized as disclosed herein can becomprised of any matrix material, or combinations thereof, and at leastone plurality of filler particles.

The selection of the particular matrix material(s) and fillerparticle(s) for use in the nanocomposite(s) will depend on the intendeduse of the medical device into which the nanocomposite will beincorporated and desired properties of a device to be used in thatmanner. The matrix material and filler particle material(s) may then bechosen, e.g., to either enhance a property of the matrix material or toadd a property otherwise absent from the matrix material so thatselected properties are exhibited by the nanocomposite, which may not beexhibited by the matrix material alone. Such an enhancement or additioncan provide the overall device with enhanced performancecharacteristics, or can provide greater quality control or enhancedtolerances in the manufacture of such devices.

Generally speaking then, the matrix material according to the inventionmay be any material suitable, or later determined to be suitable, foruse in such a medical device. The matrix material may be any materialthat is historically or currently utilized, or contemplated for futureuse, in a corresponding medical device not comprising a nanocompositecomponent. The matrix material may be comprised of organic, inorganic orhybrid organic/inorganic materials. Additionally, the matrix materialmay be a single material or a combination of materials, e.g., the matrixmaterial may be a metal alloy, copolymer or polymer blend.

Exemplary matrix materials include, for example, polymers, such asthermoplastics and thermosets. Examples of thermoplastics suitable foruse as a matrix material include, for example, polyolefins, polyamides,such as nylon 12, nylon 11, nylon 6/12, nylon 6, and nylon 66,polyesters, polyethers, polyurethanes, polyureas, polyvinyls,polyacrylics, fluoropolymers, copolymers and block copolymers thereof,such as block copolymers of polyether and polyamide, e.g., Pebax®; andmixtures thereof. Representative examples of thermosets that may beutilized as a matrix material include elastomers such as EPDM,epichlorohydrin, nitrile butadiene elastomers, silicones, etc.Conventional thermosets such as epoxies, isocyanates, etc., can also beused. Biocompatible thermosets may also be used, and these include, forexample, biodegradable polycaprolactone, poly(dimethylsiloxane)containing polyurethanes and ureas, and polysiloxanes.

Similarly, the filler particles may be comprised of any materialsuitable, or later determined to be suitable, for use in a medicaldevice as a filler. Desirably, the filler particles comprise a materialcapable of at least minimally altering the physical, mechanical,chemical, or other properties of a matrix material when incorporatedtherein. The filler particles may comprise any material that has beenhistorically used, is currently used, or is contemplated for use as aconventionally sized filler material in a medical device. Further, thefiller particles may be comprised of organic, inorganic or hybridorganic/inorganic materials.

Exemplary filler particles include, among others, synthetic or naturalphyllosilicates including clays and micas (that may optionally beintercalated and/or exfoliated) such as montmorillonite (mmt),hectorites, hydrotalcites, vermiculite, and laponite; monomericsilicates such as polyhedral oligomeric silsequioxanes (POSS) includingvarious functionalized POSS and polymerized POSS; carbon and ceramicnanotubes, nanowires and nanofibers including single- and multi-walledfillerene nanotubes, silica nanogels, and alumina nanofibers; metal andmetal oxide powders including aluminum oxide (AlO₃), titanium oxide(TiO₂), tungsten oxide, tantalum oxide, zirconium oxide, gold (Au),silver (Ag), platinum (Pt) and magnetic or paramagnetic powders such asneodinium iron boron, superparamagnetic ferrite oxide (Fe₃O₄) orsuperparamagnetic maghemite (Fe₂O₃); organic materials, includingtemperature sensitive polymers such as polyvinylpyrrolidone andn-isopropylacrylamide copolymers or blends, and poloxamer. Biodegradablepolymers may also be used, may be magnetized, if desired, and include,for example, poly(lactic)acid, polysaccharide, andpolyalkycyanoacrylate.

The present invention contemplates that there may be applications inwhich it will be desirable to have a combination of more than oneplurality of filler particles, so that each different plurality may becomprised of a different material. In this manner, a further enhancementof a single desired property, or a new property broadening the array ofproperties, may be seen in the medical device prepared from such ananocomposite. For example, it may be advantageous to prepare ananocomposite from a polymeric matrix material, a first filler particlematerial that exhibits radio-opacity, and a second filler particlematerial that is influenced by magnetic fields. As a result, a medicaldevice in accordance with the present invention may incorporate morethan one plurality of nanoparticulate filler particles, wherein eachplurality may comprise a different material.

As mentioned above, the filler particles used in the nanocompositesaccording to the invention can be comprised of any material utilized ina medical device as a conventionally sized filler. While suchconventionally sized filler particles can range in size from severalmicrons to several millimeters in size, the filler particles utilized innanocomposites are desirably 1000 nm in the greatest dimension or less,more optimally, 750 nm or less, typically 500 nm or less, for example,from about 1 nm to about 100 nm. It is believed that the smaller theparticle, the more easily dispersed within the matrix material it willbe, and as a result, in embodiments where a uniform dispersion isdesired, it is preferred that the particles are 100 nm or less in thegreatest dimension.

Further, the filler particles, whatever material they are comprised of,may be of any shape, i.e., the filler particles can be generallyspherical, octagonal or hexagonal, or they may be in the form ofnanotubes, nanobelts, nanofibers, nanowires, etc. However, and as ismentioned above, the dispersion of the filler particles within thematrix material, as well as the interaction of the matrix material andthe filler particles, may be enhanced by increasing the surface areacontact between the matrix material and the filler particles, and assuch, filler particles having a high aspect ratio, i.e., a large ratioof their lateral dimension to their thickness, may be particularlyadvantageous. For example, and whatever the geometry of the fillerparticle, it is contemplated that filler particles having aspect ratiosof greater than 20:1 will be capable of promoting this increaseddispersion and/or interaction between the filler particles and thematrix material. In some embodiments, the filler particles willdesirably have aspect ratios of between 50:1 and 2500:1, typicallybetween 200:1 and 2000:1, for example, from 300:1 to 1500:1.

The amount of the filler particles, or combinations of filler particlescomprised of different materials, to be incorporated into the matrix canvary depending on the desired properties exhibited by a particularmedical device or medical device component. Generally speaking, enoughof the particles should be included so that desired properties are atleast minimally exhibited by the nanocomposite, but not so much of thefiller particles should be included so as to have a detrimental effecton the properties of the nanocomposite. While the particular range mayvary depending on the filler particles and matrix material beingutilized, nanocomposites exhibiting advantageous properties can beobtained by incorporating from about 0.005% to about 99% nanoparticlesrelative of the total final composition weight of the nanocomposite. Inmany embodiments, nanoparticles may be incorporated in an amount of fromabout 0.01% up to about 40% or 50% by weight of the nanocomposite. In atypical embodiment, the nanoparticles can be incorporated in an amountof from about 0.1% to about 20% of the nanocomposite, for example, fromabout 1% to about 10% by weight of the nanocomposite.

The properties of the nanocomposites may be affected by compatibilityof, and/or the level and/or kind of interaction that occurs between, thefiller particles and the matrix material of the nanocomposite. Thecompatibility of the filler particles and the matrix material may beminimal e.g., so that the interaction therebetween is limited tophysical contact that occurs when the filler particles are simplydispersed within the matrix. Or, the compatibility may be such that thefiller particles and the matrix interact physically, such as by chainentanglement of the filler particles with the matrix material. Thefiller particles and matrix material may also interact chemically, suchas by the establishment of Van Der Waal's forces, covalent bonds orionic bonds between the filler particles and the matrix material.

Generally speaking, any such compatibility, and the resultinginteraction, can act to enhance the dispersion of the filler particleswithin the matrix material and/or to further enhance the properties ofthe nanocomposite as compared to a corresponding traditionally filledpolymer. If this is the case, and very generally speaking, the greaterthe compatibility and more or stronger the interaction, the greater theincreased dispersion and/or enhancement. Therefore, in applicationswhere such greater dispersion or further property enhancement would bedesirable, the compatibility of, and resulting interaction between, thefiller particles with the matrix material can be encouraged orfacilitated.

The compatibility of the filler particles and the matrix material can beenhanced, for example, simply by selection of the materials for use asthe matrix or in the filler particles. That is, interaction between thefiller particles and the matrix may be facilitated simply by selectingfiller particles and matrix materials with compatible functional groups.If such compatible functional groups are not present, they can beprovided by “functionalizing” the filler particles or matrix material toprovide compatible functional groups that can then interact with eachother. Phyllosilicates, monomeric silicates and ceramics are just a fewexamples of materials suitable for use in the filler particles that maybe advantageously functionalized to provide increased interactionbetween the filler particles and the matrix material.

For example, POSS monomers can be functionalized with, e.g., organicside chains to enhance compatibility with, e.g., polystyrene. Theceramic boehmite (AlOOH) already has many surface available hydroxylgroups and, as such, may be further functionalized with, e.g.,carboxylic acids, which in turn can be functionalized to interact withfunctional groups within the matrix material. Additionally, clays suchas aluminosilicates or magnesiosilicates can be functionalized withblock or graft copolymers wherein one component of the copolymer iscompatible with the clay and another component of the copolymer iscompatible with the polymer matrix. Or, clays such as montmorillonitemay be functionalized with alkylammonium so that the clay is capable ofinteracting with a polyurethane, for example.

Advantageously, in those embodiments of the invention wherein thenanocomposite is desirably utilized in a multi-layered medical device,such as multi-layered tubing, and wherein at least two layers of themulti-layered device desirably comprise nanocomposite materials,functionalizers can be chosen for each layer that allow for the furtheroptimization of the desirable properties of that layer, whilepotentially reducing compatibility issues between the layers. That is,in such embodiments of the invention, the at least two layers maycomprise a nanocomposite material further comprising the same matrixmaterial, or compatible matrix materials, and the same filler particles,but yet incorporating different functionalizers. The layers will thus bechemically compatible and easily coprocessed, and yet may exhibitdifferent desirable properties.

In addition to functionalizing either or both the filler particlesand/or matrix material, the compatibility of, and interaction between,the filler particles and matrix material can be enhanced byincorporating one or more coupling or compatibilizing agents into thenanocomposite to be used in the inventive medical devices. Whereasfunctionalizers, discussed above, generally increase compatibility bymodifying either or both of the matrix material and filler particles toinclude compatible chemical groups in their respective structures,coupling or compatibilizing agents need not do so in order to effectuatesuch interaction. That is, suitable coupling/compatibilizing agents foruse include any agent capable of enhancing compatibility and/orpromoting interaction between the filler particles and the matrixwithout necessarily structurally modifying either or both the fillerparticles or matrix material. Such agents can be organic or inorganic.

The selection of these optional agents will, of course, depend on thematrix and filler particle materials selected. Bearing this in mind,suitable organic coupling agents can be both low molecular weightmolecules and polymers. Examples of low molecular weight organiccoupling/compatibilizing agents include, but are not limited to, aminoacids and thiols. For example, 12-aminododecanoic acid may be used tocompatibilize clay within any desired thermoplastic matrix. Examples ofpolymeric compatibilizers include functionalized polymers, such asmaleic anhydride containing polyolefins or maleimide-functionalizedpolyamides. One example of a nanocomposite wherein the compatibility maybe enhanced via the inclusion of such a polymeric compatibilizer wouldbe a polyolefin or nylon 12/montmorillonite nanocomposite, which mayfurther include an amount of maleic anhydride functionalizedpolypropylene to compatibilize the matrix material and filler particles.Inorganic coupling agents would include, for example, alkoxides ofsilicon, aluminum, titanium, and zirconium, to name a few.

Generally speaking, the amount of a coupling/compatibilizing agent used,if used at all, will desirably be that amount which will at leastmarginally improve the compatibility of the filler particles and thematrix material so that at least a minimal enhancement of the dispersionof the filler particles within the matrix and/or the properties of thenanocomposite can be observed. Useful amounts of such agents arecontemplated to be within the ranges of from about 0.01% to about 10% byweight of the nanocomposite; typically from about 0.05% to about 5.0%,more typically from about 0.1% to about 1% by weight of thenanocomposite.

In addition to material selection, functionalizing and/or the use ofcompatibilizing agents as a means to promote interaction of the fillerparticles throughout the matrix material, the dispersion of the fillerparticles may be enhanced, if desired, by utilizing ultrasonic assistedextrusion and/or compounding. That is, by applying an ultrasonicvibration to the extruder die, the friction shear forces can be reducedand the melt rendered more homogeneous. More particularly, such anextruder could include, e.g., an extruder head capable of extruding apolymer melt having an ultrasonic transducer operatively disposedthereto. The ultrasonic transducer would be capable of transmittingultrasonic waves to the extruder head, which waves may furtheradvantageously be modulated to include at least one amplitude andmodulation. In this manner, the waves provided to the extruder head may,if desired, be provided as substantially uniform vibrations tosubstantially the entirety of the extruder head.

An additional method for enhancing the dispersion of the fillerparticles throughout the matrix material could include dispersing thefiller particles in a solvent, e.g., dimethylformamide,dichloroethylene, N-methyl-2-pyrrolidone, and the like. Once sodispersed, the filler particles could be mixed with a similarlydissolved matrix material and sprayed onto a mandrel to produce ananocomposite material with enhanced dispersion of the filler particles.Any other known techniques of enhancing the dispersion of fillerparticles within a matrix can also be utilized, if such an enhanceddispersion is desirable in the chosen application.

If dispersion of the matrix material and/or filler particles within asolvent is desired, either or both of the matrix material or fillerparticles may be functionalized in order to effectuate theirdispersability within a desired solvent. That is, in addition tofunctionalizing either or both of the matrix material and/or fillerparticles so that they are more compatible with one another once formedinto a nanocomposite material, either or both of the matrix materialand/or filler particles may be functionalized to effectuate theirdispersability within a solvent, in order to further enhance thedispersability of the filler particles within the matrix material. Asbut one example of this embodiment of the present invention,single-walled carbon nanotubes may be functionalized with, e.g.,carboxylic acid groups that are then subsequently converted to acylchloride, followed by conversion to an amide, to render the nanotubesdispersable in organic solutions. As an additional example,functionalization with mono-amine terminated poly(ethylene oxide) orglucosamine can render single walled carbon nanotubes soluble in aqueoussolutions. Such functionalization of nanotubes to enhance theirdispersion within aqueous or organic solvents is described in, e.g.,U.S. Pat. Nos. 6,331,262 and 6,368,569, as well as Pompeo and Resasco,“Water Solubilization of Single Walled Carbon Nanotubes byFunctionalization with Glucosamine” Nano Letters, 2(4), pp 369-373(2002) and Bandyopadhyaya et al., “Stabilization of Individual CarbonNanotubes in Aqueous Solutions”, Nano Letters, 2(1), pp 25-28 (2002),the entire disclosures of each being hereby incorporated by referenceherein.

While it may be desirable in certain applications to increase theinteraction between the nanoparticles and the matrix material, orbetween the nanoparticles and the device itself, extensive interactionbetween the nanoparticles themselves can be undesirable in certainapplications. In particular, in applications where the nanoparticlesdesirably form a layer with a substantially uniform thickness, or wherean otherwise substantially uniform dispersion throughout a matrixmaterial or relative to a medical device is desired, any substantialagglomeration of the nanoparticles can be suboptimal. In suchapplications then, it may be advantageous or desirable to include adispersant in solution with the nanoparticles prior to their dispersionwithin, or application to, the matrix material and/or the inventivedevice.

As but one example of this aspect of the invention, and in thatembodiment wherein the nanoparticles desirably comprise carbonnanoparticles, such as carbon nanotubes, natural carbohydrates may beutilized to minimize or eliminate the interactions between the carbonnanotubes that may otherwise occur when the nanotubes are desirablysolubilized. See, e.g., Dagani, “Sugary Ways to Make NanotubesDissolve”, Chemical and Engineering News, 80(28), pages 38-39; and Staret al., “Starched carbon nanotubes” Angewandte Chemie-InternationalEdition, 41(14), pp. 2508 (2002), the entire disclosures of which areincorporated by reference herein.

In particular, in order to provide a solution of substantiallynon-aggregated carbon nanotubes that may then be mixed with a similarlydispersed matrix material or simply applied to a matrix material byspraying or dipping, the carbon nanotubes may be dispersed in an aqueoussolution comprising such a natural carbohydrate. Illustrative examplesof such natural carbohydrates include, but are not limited to, starches;gums, e.g., gum arabic, and sugars gum. This solution can then be driedto form a substantially non-aggregated powder of carbon nanotubes andgum arabic that may then be compounded with a matrix material andprocessed into the desired medical device according to conventionaltechniques, or the solution may be used to create uniform layers ofsubstantially non-aggregated carbon nanotube fibers on the surface of amatrix material, on the surface of a component of a medical device, oronto substantially the totality of a surface of a medical device inorder to provide a medical device in accordance with the presentinvention. If a uniform layer is desired, once the carbon nanotube/gumarabic solution has been prepared, the desired material may simply becoated with the solution by dipping the material in the solution andallowing the water to evaporate, leaving behind a substantially uniformlayer of substantially non-aggregated carbon nanotubes. As discussedhereinabove, if desired, the carbon nanotubes can advantageously befunctionalized prior to any such dispersion.

Such a layer of carbon nanotubes may be used as a tie layer betweenpolymer layers of a medical device, e.g., by depositing the carbonnanotubes as described on at least one of the surfaces to be thermallybonded. Upon thermal bonding of the two layers, the interspersed tielayer of carbon nanotubes would provide additional reinforcement to thebond site. This advantageous technology may be applied to embodimentswhere a tie layer is desired between two layers of material wherein thesecond layer of material is applied to the first via welding, spraying,or multilayer extrusion and/or wherein electrical conductivity isdesired. In such embodiments, the carbon nanotube/gum arabic solutionwould simply be applied to the first material and allowed to dry, andthe second material subsequently applied according to the desiredtechnology over the substantially uniform carbon nanotube layer.Further, the physical interaction between the carbon nanotubes and thematrix material can be supplemented by functionalizing the arabic gumwith functionalizers as described above, providing a further opportunityto reinforce the bond site.

In addition to the filler particles, the matrix material and,optionally, a coupling/compatibilizing agent, the nanocompositesaccording to the invention can comprise any other materials utilized ina corresponding medical device not comprising a nanocomposite. Forexample, pigments and/or whiteners, and/or conductive, magnetic and/orradiopaque agents could be provided in the nanocomposites, if desired.Also processing aids, such as plasticizers, surfactants and stabilizers,can be included in the nanocomposites. Such agents, the amounts in whichthey are useful, as well as the benefits that they provide, are wellknown to those of ordinary skill in the art.

One example of a class of stabilizers that may find use in the inventivemedical devices and methods is that commonly referred to as radiationoxidative degradations, or “ROD” stabilizers. As the name suggests,these agents may assist a polymer within which they are incorporated toresist any degradation that may otherwise occur upon exposure of thepolymer to sterilizing radiation. Additionally, however, suchstabilizers may also be useful in assisting a polymer to resist anydegradation that may otherwise occur during processing, such as duringmixing and/or heating that may be required in order to adequatelydisperse nanoparticles throughout a matrix material.

Such ROD stabilizers may be antioxidants, particularly radical or oxygenscavengers. Mercapto compounds, hindered phenols, phosphites,phosphonites and hindered amine antioxidants are among the mosteffective such stabilizers. Specific examples of stabilizers are2-mercaptobenzimidazole, trilauryl phosphite, IONOX 330,2-mercaptobenzothiazole, N,N-di(β-napthyl-p-phenylenediamine) (DPPD),SANTONOX R, SANTOWHITE powder, phenothiazine, IONOL,2,6-di-t-butylcresol, N-cyclohexyl-N′-phenyl-p-phenylenediamine, nickeldibutyldithiocarbamate, IRGANOX 1010, β-(3,5-di-t-butyl-6-hydroxyphenyl)propionate, 1,2,2,6,6-pentamethyl-4-stearoyl piperidine, and 2,2,6,6,tetramethyl-4-nitropiperidine. Further examples include butylatedreaction product of p-cresol and dicyclopentadiene, substituted amineoligomers,N,N′-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine,2,4-dichloro-6-(4-morpholinyl)-1,3,5-triazine, andN,N′-hexamethylene-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide].Still further, transition metals or compounds thereof may function asROD stabilizers, for instance iron, cobalt, nickel, ruthenium, rhodium,palladium, osmium, iridium, platinum, copper, manganese and zinc metaland compounds, as described in International Pub. No. WO 99/38914, U.S.Pat. No. 5,034,252 and U.S. Pat. No. 5,021,515.

The ROD stabilizer may also be an oxygen scavenging polymer, such as thepolyketone polymers described in International Pub. No. WO 96/18686 ofthe formula

where R is H, an organic side chain or a silicon side chain, and n is apositive number greater than 2. Such polyketone ROD stabilizers aresuitably employed in the thermoplastic composition in an amount of from0.1 to about 10% by weight.

If their presence is desired, ROD stabilizers may be employed in thenanocomposites in any amount at least minimally effective in assistingin the resistance of the matrix material to degradation, i.e., inamounts of from about 0.01% to about 5%, suitably from about 0.1 toabout 1%, for instance from 0.2% to 0.5%. The stabilizer can becompounded into the nanocomposite in the extrusion melt or in a separatecompounding step prior thereto.

Many nanocomposites and nanoparticles are commercially available.Additionally, many methods of producing nanocomposites and/ornanoparticles are known, and any of these can be utilized to producenanocomposites and nanoparticles for incorporation into the inventivemedical device. Many such methods are disclosed and described, forexample, in “Nanocomposites 2001, Delivering New Value to Plastics”,Executive Conference Management, Jun. 25-27, 2001, Chicago, Ill., theentire disclosure of which is incorporated by reference herein.

Advantageously, and since the filler particles can have an impact on theproperties exhibited by the nanocomposite by virtue of the dispersion ofthe filler particles within the matrix, the particular method utilizedto prepare the nanocomposite can be selected to assist in the provisionof a medical device with the desired array of properties. That is, incertain medical device applications, it may be desirable to have theentirety of the medical device or medical device component exhibit theproperties of the nanocomposite substantially uniformly throughout, oracross the length of, the medical device. In such applications, it wouldbe desirable to substantially uniformly distribute the filler particlesthroughout the matrix of the nanocomposite. In other applications, itmay be desirable to have the entirety of the medical device or medicaldevice component exhibit the properties of the nanocomposite, but atvarying degrees throughout the device or component. In theseapplications, then, it would be desirable to vary the distribution ofthe filler particles throughout the matrix of the nanocomposite in amanner so that the desired varied properties are observed in the medicaldevice or component.

For exemplary purposes only, then, processes for the production of suchnanocomposites include polymerization of the matrix material in thepresence of the filler particles, melt compounding of the matrixmaterial with the filler particles, and in-situ formation of the fillerparticles, e.g., as would be provided by the adding a silane monomer toa block copolymer and then curing the silane to produce nanostructuredsilica filler particles relatively uniformly dispersed within the matrixmaterial of the copolymer, to name a few. If a coupling/compatibilizingagent is to be used, it may be pre-coated onto the filler particlesbefore compounding the filler particles with the matrix, oralternatively, the agents may be added during the nanocompositeformation process.

Generally, one of the advantages of the utilization of nanocomposites isthat, at least as compared to traditionally filled polymers,nanocomposites are often more easily processed. As a result, once thenanocomposite has been prepared, it can be processed into the desiredmedical device by any method known to those of ordinary skill in theart, and the particular method chosen is not critical to the practice ofthe present invention. There are a multiplicity of methods for themanufacture of medical devices that are thus appropriate, examples ofwhich include, but are not limited to, foam processing, blow molding orfilm molding, sheet forming processes, profile extrusion, rotationalmolding, compression molding, thermoset pre-preg processes and reactioninjection molding processes. Of course, the inventive medical device canbe manufactured by any method utilized to manufacture a correspondingmedical device not comprising a nanocomposite.

The invention will now be further illustrated in the following examples,which are not intended to be limiting, but rather have been chosen anddescribed so that others skilled in the art may appreciate andunderstand the principles and practices of the present invention.

Example 1 Preparation of Inner Shaft Catheter Tubing with an HDPE/POSSNanocomposite 1) Preparation of the HDPE/POSS Nanocomposite byTwin-Screw Extrusion Compounding

An organically functionalized POSS (MS0830, an OctaMethyl-POSScommercially available from Hybrid Plastics, Fountain Valley, Calif.)was compounded with high density polyethylene (HDPE Marlex 4903,commercially available from Chevron-Phillips Chemical Company, Houston,Tex.). In particular, a material feed ratio of HDPE to POSS of 4:1 wasfed into a counter rotating dispersive twin screw compounder ZSSE 27(commercially available from Leistritz Company, Allendale, N.J.)operating at 190° C. and a speed of 200 RPM. The compounding output wasat 5 pounds per hour.

2) Extrusion of Inner Shaft Catheter Tubing Incorporating HDPE/POSSNanocomposite Material

A 4:1 mixture of the HOPE/POSS nanocomposite to Plexar 390 anhydridemodified polyethylene (commercially available from Equistar ChemicalCompany, Houston, Tex.) was premixed and then further diluted at a 3:1ratio with Marlex 4903 polyethylene and extruded into tubing ofdimensions of 0.018 inch×0.024 inch at 220° C. The resulting inner shafttubing could be used in an over the wire, single operator exchangecatheter, or stent delivery system using conventional constructiontechniques.

Example 2 Preparation of Outer Shaft Catheter Tubing with a Pebax®/POSSNanocomposite 1) Preparation of the Pebax®/POSS Nanocomposite byTwin-Screw Extrusion Compounding

An organically functionalized POSS (AM0265, an Aminopropylisobutyl-POSScommercially available from Hybrid Plastics) was compounded withPebax®7233 (Pebax® is a polyether block amide commercially availablefrom Atofina, Brussels, Belgium). In particular, a material feed ratioof Pebax® to POSS of 4:1 was fed into a counter rotating dispersiveLeistritz ZSE 27 twin screw compounder operating at 200° C. and a speedof 100 RPM. The compounding output was at 5 pounds per hour.

2) Extrusion of Outer Shaft Catheter Tubing Incorporating Pebax®/POSSNanocomposite Material

A 3:1 dilution of the Pebax®/POSS nanocomposite to Pebax®7233 wasprepared and extruded into outer shaft tubing with dimensions of 0.0306inch×0.0362 inch at 226° C.

During the tubing extrusion process, the nanocomposite may be morestable than conventional filled Pebax®. If the tubing produced by thismethod were subject to an EtO sterilization, that the POSS nanofillerwill reduce or substantially prevent the oriented Pebax® chains fromrelaxing to a detrimental degree, as compared to such relaxation thatwould be expected to occur in an unfilled Pebax® medical device ordevice component when subjected to such sterilizing treatment.

Example 3 Preparation of Outer Shaft Catheter Tubing with a Pebax®/ClayNanocomposite

A Pebax®/clay nanocomposite material said to contain 95% Pebax® 7233 and5% clay filler with the trade designation of 2099×83109 C was purchasedfrom RTP Company (Winona, Minn.). The material was extruded intoacceptable outer shaft tubing with dimensions of 0.0306 inch×0.0362 inchat an extrusion temperature of 226° C.

Example 4 Preparation of Multilayer Tubing with a Pebax®/MontmorilloniteNanocomposite

A Pebax®/montmorillonite nanocomposite material containing 95% of a 72durometer Pebax® material (such as Pebax® 7233 commercially availablefrom Atochem) and 5% montmorillonite filler will be compounded with atwin screw extruder as described above. The nanocomposite material willthen be coextruded with non-filled Pebax® at a temperature sufficient toprovide appropriate viscosity for extrusion, i.e., from about 190° C. toabout 215° C., into acceptable trilayer tubing having thePebax®/montmorillonite nanocomposite as a middle layer and non-filledPebax® as the inner and outer layers. The trilayer tubing will havedimensions appropriate for the intended use of the tubing. If the tubingis to be used, e.g., in the formation of a balloon, suitable dimensionswould be an inner diameter of about 0.0176 inch and an outer diameter ofabout 0.342 inch.

Example 5 Preparation of Monolayer Tubing with a Pebax®/ModifiedMontmorillonite Nanocomposite

A Pebax®/montmorillonite nanocomposite material containing 90% of a 70durometer Pebax® material (such as Pebax® 7033 commercially availablefrom Atochem) and 10% modified montmorillonite filler will be compoundedwith a twin screw extruder as described above. Prior to compounding, themontmorillonite will be modified with a functionalizer comprising ablock copolymer capable of interacting with polyether and/or polyamide,as described hereinabove. The nanocomposite material will be extruded ata temperature sufficient to provide appropriate viscosity for extrusion,i.e., from about 190° C. to about 215° C., into acceptable monolayertubing having dimensions appropriate for the intended use of the tubing.This tubing can then be used to form balloons, the inner lumen ofcatheters, the outer lumen of catheters, and the like. If the tubing isto be used, e.g., in the formation of a balloon, suitable dimensionswould be an inner diameter of about 0.0176 inch and an outer diameter ofabout 0.342 inch.

Example 6 Preparation of Monolayer Tubing with a Nylon 12/ModifiedMontmorillonite Nanocomposite

A nylon 12/montmorillonite nanocomposite material containing 99% of anylon 12 (commercially available under the trade name Rilsan® fromAtofina) and 1% modified montmorillonite filler will be prepared asfollows. All materials will either be purchased as powders or groundinto powders by any known method. The montmorillonite will be modifiedwith a functionalizer comprising block polyamide or any material havingpolyamide groups, as described hereinabove. The powdered nylon 12 andpowdered functionalized montmorillonite will be mixed together and fedinto an extrusion process via a gravimetric feeding device (or any otheracceptable powder feeding mechanism). The nanocomposite material willthen be extruded at a temperature sufficient to provide appropriateviscosity for extrusion, i.e., from about 210° C. to about 240° C.,typically 220° C. to 230° C., into acceptable monolayer tubing havingdimensions appropriate for the intended use of the tubing. Such usescould include, e.g., formation of balloons, inner lumens of catheters,outer lumens of catheters, etc. Tubing comprising such a nanocompositeis contemplated to be particularly useful in the formation of balloons,for which use appropriate tubing dimensions are an inner diameter ofabout 0.0176 inch and an outer diameter of about 0.342 inch. Moreparticularly, the balloon could be formed by any known method andsubsequently attached to catheter shafting by any known constructionmethod.

Example 7 Preparation of Heat Bonded Multilayer Catheter ShaftingComprising a Single Walled Carbon Nanotube Tie Layer

Multilayer catheter shafting will be prepared comprising a layer ofPebax® and a layer of Plexar® (anhydride modified polyethylenecommercially available from Equistar Chemical Company, Houston, Tex.),having a tie layer of single walled carbon nanotubes therebetween usingan over-the-wire tandem extrusion process as follows:

Plexa® will be extruded onto a Teflon coated copper mandrel at 220° C.An aqueous solution of arabic gum and single wall carbon nanotubes (1 mlpurified water, 200 mg gum arabic, 30 mg carbon nanotubes) will then besprayed onto the Plexar® shafting. Any excess water will be removed byrunning the shafting through a 120° C. oven. A second extruder in tandemwill extrude a layer of Pebax® over the Plexar carbon nanotubes at atemperature of 226° C. The resulting multilayer tubing will exhibitenhanced bond strength between the layers due to the embedment of thecarbon nanotubes at the interface layer.

Example 8 Effect of Different Functionalizers on Performance andProperties of Pebax®/Clay Nanocomposites

Three nanocomposites were prepared comprising 95% Pebax® 7233 and 5%clay. More particularly, a first such nanocomposite comprisingunmodified clay, a second such nanocomposite comprising clay modifiedwith a block copolymer having hydroxyl end groups and a third suchnanocomposite comprising clay modified with a block copolymer havingcarboxylic end groups were separately compounded with a twin screwextruder as described above. The material was extruded into tubing andtested on an Instron. The elongation at break (epsilon), elasticitymodulus (E) as well as the ultimate strength (sigma) were measured. Theresults are provided below in Table 1:

TABLE 1 E(N/mm²) Sigma (N) Epsilon % Unmodified clay/Pebax ® 576.741.0666 128.94 nanocomposite ROH modified clay/Pebax ® 669.3 42.96667200.8667 nanocomposite RCOOH modified clay/Pebax ® 650.1 44.225 152.755nanocomposite

As is shown, the properties of the modified clay nanocomposites varysignificantly. In order to take advantage of this variation, forexample, the ROH modified clay/Pebax® nanocomposite could be used as anouter layer for a balloon, thereby obtaining an increase ofapproximately greater than 50%, typically greater than 40%, for examplegreater than 25%, in puncture resistance due to the increase in epsilon.If the RCOOH modified clay/Pebax® nanocomposite were then utilized as aninner layer of the same balloon, the burst resistance could be increasedas a result of the measured increase in overall strength that was seenin this nanocomposite relative to a nanocomposite comprising anunmodified clay.

Referring now to FIGS. 1 and 2, there is illustrated an embodiment of amedical device according to the invention. In particular, FIG. 1 is alongitudinal cross-sectional view of the distal end of a balloonangioplasty catheter 10. In this embodiment, catheter 10 includes aninner tubular component 1 comprising an inner layer 2 and outer layer 3.A balloon 4 having a distal waist 5 is attached to inner tubularcomponent 1. Balloon 4 also has a proximal waist 6 attached to outertubular component 7. A guidewire 11 is shown within lumen 12 of innertubular member 1. FIG. 2 is a transverse cross-sectional view taken atline 2-2 of FIG. 1.

According to the invention, it will be appreciated that inner tubularcomponent 1, inner layer 2, outer layer 3, balloon 4, or outer tubularcomponent 7, or guidewire 11, can be prepared in whole or in part from ananocomposite material as disclosed herein. In addition, any of thesecomponents can be a single layer or a multiple layer with one or more ofthe layers comprising a nanocomposite. Thus, for example, in FIGS. 1 and2, inner tubular component 1 is illustrated with multiple layerswherein, either or both of layers 2 and 3 of inner tubular component 1can be prepared from a nanocomposite material. Thus, for example, eitherof layers 2 or 3 can comprise a nanocomposite material prepared asdescribed in Examples 1-3 above. In other embodiments, referring to FIG.3, inner tubular component 1 includes two nanocomposite layers 15, 15′and a normanocomposite layer 17 between the nanocomposite layers. Asshown, nanocomposite layer 15 and normanocomposite layer 17 are tapered,and balloon 4 includes two layers 19, 21. Either or both of layers 19,21 can be prepared from a nanocomposite material, as indicated above.

Also as disclosed earlier, a stent delivery system including the stentmounted over balloon 4 can be prepared according to the invention. Inaddition, components known in the art for use with balloon expandablestent delivery systems, such as sleeves, disclosed for example in U.S.Pat. No. 4,950,227 can be used. Based on this disclosure, it will beappreciated that self-expanding stent delivery systems, guide catheters,angiography catheters, etc., can also be prepared within the scope ofthe invention.

Other embodiments of this invention will be apparent to those skilled inthe art upon consideration of this specification or from practice of theinvention disclosed herein. Various omissions, modifications, andchanges to the principles and embodiments described herein may be madeby one skilled in the art without departing from the true scope andspirit of the invention which is indicated by the following claims.

1. An intravascular balloon catheter comprising: an outer tubularmember; an inner tubular member disposed coaxially within the outertubular member, the inner tubular member defining a guidewire lumen; andan inflatable balloon having a proximal waist and a distal waist,wherein the balloon is attached to the outer tubular member at theproximal waist and the balloon is to the inner tubular member at thedistal waist; wherein at least a portion of the outer tubular membercomprises a nanocomposite material.
 2. The balloon catheter of claim 1,wherein the nanocomposite material comprises a matrix material and atleast one plurality of nanoparticles.
 3. The balloon catheter of claim2, wherein the matrix material comprises a thermoplastic or a thermosetpolymer.
 4. The balloon catheter of claim 3, wherein the matrix materialcomprises nylon
 12. 5. The balloon catheter of claim 2, wherein thenanoparticles comprise a clay.
 6. The balloon catheter of claim 5,wherein the clay comprises montmorillonite.
 7. The balloon catheter ofclaim 5, wherein a quantity of nanoparticles varies along a longitudinalaxis of the outer tubular member.
 8. The balloon catheter of claim 7,wherein a flexibility of the outer tubular member varies with thequantity of nanoparticles.
 9. The balloon catheter of claim 2, whereinthe nanocomposite further comprises a functionalizer.
 10. The ballooncatheter of claim 9, wherein the functionalizer is alkylammonium.
 11. Anintravascular balloon catheter comprising: an outer tubular member; aninner tubular member having at least an inner layer and an outer layer,the inner tubular member disposed coaxially within the outer tubularmember; and an inflatable balloon having a proximal waist and a distalwaist, wherein the balloon is attached proximate the distal end of theouter tubular member at the proximal waist and the balloon is attachedproximate the distal end of the inner tubular member at the distalwaist; wherein at least a portion of the outer tubular member comprisesa nanocomposite material.
 12. The balloon catheter of claim 11, whereinthe nanocomposite material comprises a thermoplastic or thermoset matrixmaterial and at least one plurality of nanoparticles.
 13. The ballooncatheter of claim 12, wherein the nanoparticles comprise a clay.
 14. Theballoon catheter of claim 11, wherein at least one of the inner layerand the outer layer of the inner tubular member each comprise ananocomposite material.
 15. The balloon catheter of claim 11, wherein aportion of the outer tubular member comprises a material other than ananocomposite
 16. The balloon catheter of claim 11, wherein the innertubular member further comprises a third layer disposed between theinner and outer layer.
 17. The balloon catheter of claim 12, wherein thenanoparticles comprise carbon or ceramic nanotubes or fibers.
 18. Theballoon catheter of claim 12, wherein the nanocomposite materialcomprises a combination of more than one plurality of nanoparticles. 19.The balloon catheter of claim 12, wherein the nanocomposite materialfurther comprises a functionalizer.
 20. An intravascular ballooncatheter comprising: an outer tubular member; an inner tubular memberhaving an inner layer and an outer layer, the inner tubular memberdisposed coaxially within the outer tubular member; and an inflatableballoon having a proximal waist and a distal waist, wherein the balloonis attached to the outer tubular member at the proximal waist and theballoon is attached to the inner tubular member at the distal waist;wherein at least a portion of the outer tubular member is comprised of ananocomposite material, the nanocomposite material including a matrixmaterial comprised of nylon 12, at least one plurality of nanoparticlescomprised of a clay, and a functionalizer; wherein the quantity ofnanoparticles varies along a longitudinal axis of the outer tubularmember so as to vary a flexibility of the outer tubular member.